Compressed-air brake



Aug. 12, 1930. w HlLDEBRAND Q 1,772,832

COMPRESSED AIR BRAKE Filed Nov. 30. 1928 2 Sheets-Sheet l A g- 1930- w.HILDEBRAND 1,772,832

COMPRESSED Magnum I Filed Ndv. 30, 1928 2 Sheets-Sheet 2//////////////////////,7// Z'// ////////////////I//17I////////'V 1/llllI-l Patented Aug. 12, 1930 pairs!) STATES PATENT OFFICE WILI-IELMHILDEBRA-ND, F BERLIN, GERMANY:

COMPRESSED-AIR BRAKE Application filed November 30,1928, Serial No.322,42, and in Germany November 1, 1927.

case of leakagesoccuring in the said cyl- :inder.

Singlec hamber compressed air brakes are already known, wherein thegraduation of the releasing process is efiected by means of a specialdevice added to the usual braking installation. In these known brakesthe additional effect of'the special device is limited to the release ofthe air from the brake cylinder, and they do not present the possibilityof an automatic replenishing in case of a fall in the brake cylinderpressure due to leakage in the cylinder.

Inthe case of control valves wherein the control of the pressure in thebrake cylinder is effected by valves operated by means of the said'pressure, the control members used 5 are subjected on both sides todifferent pressuresQ The control members must therefore 7 be at alltimes absolutely tight against any pressure difference. For such workingcon ,ditions the known control pistons provided with a packing ring andeasily displaceable are not suitable because the packing ring is 'not,absolutely tight. lVith brakes of the above mentioned kind: it hastherefore been necessary 'to'employ diaphragms, or, case of long;control paths, pistons packed with leather rings. Owing to theconsiderable friction of the packing rings, suchpistons are notsensitive to small'pressure differences, and the packing rings owing totheir content of fat become stiif in winter, and may possi'bly freeze onto the cylinder walls. The requisite sensitiveness of the brakes is thusadverselyafl'ected to a considerable degree.

In the case of control pistons that are only temporarily exposed topressure differences, and Where an equalization of the pressures soontakes place, such a packing is not essential, consequently the knownsplit packing ring i s eniployed; this packing although'not absolut ytight, does not prevent the cont ol piston from being sensitive topressure clifferences. Because of the leakage permitted by their easy"Working, however, such pistons are not "suitable for control valves onbrakes of known types where a fine graduation of the braking and releaseprocesses is required.

According to the present invention a primary control valve has an easilymoving piston which is on the one side exposed to the train pipepressure and on the other side to the pressure of a regulating aircontainer, the filling and exhaustion of which container are governed bythe said primary control valve,

so that the piston of the said valve is only the opposite direction; thecontrol members in this secondary con- The movements of trol valve whichefiect the application and release of the brake are caused byalterations in the pressure of the regulating container, which pressureis dependent on the movements of the highly sensitive primary controlvalve in accordance with the variations of pressure in the train pipe.The operative members of this secondary control valve may comprise,differential pistons, namely, a main piston connected with a slide andexposed on one side to the container pres sure, and a separate pistonexposed to brake cylinder pressure supporting the'action of thecontainer pressure on the main piston, this main piston being on itsother side exposed to a'pressure'inthe control chamberofthe secondaryvalve opposing the two first mentioned forces.

In order that the said invention may be clearly understood and readilycarried into effect the same will now be described more fully withreference to-the accompanying diagramsillustrating four diiferentconstructional od men s of in tion, Fla

ures 1 to it In the embodiment according to Figure 1 the train pipe L isconnected by pipes L, L with the interior of the casing of the primarycontrol valve St-. The primary control valve i comprisesa piston c?oneratively fic lll r d W with a hollow slide S which slide normallycovers an aperture 0 opening to the atmosphere. The regulating aircontainer II is at one end connected by a pipe 6 with the space A behindthe piston [0 and is at its other end connected by av pipe 6 with theinterior of the primary control valve casing at a point adjacent to themouth of the pipe L the mouths of the pipes b and L both opening intothe hollow of the slide S when this slide is in the normal or releaseposition as inclicated in the drawing. In the regulating container H isformed a sleeve is", in which can work a small piston 72 on the rod of apiston K, the latter piston dividing the interior of the container Einto two chambers A and B, the capacities of these chambers A, B, beingvariable according to the movements of the piston K.

The secondary control valve S3 comprises a central chamber B a widerchamber A and a compartment 0 separated from the said central chamber bya partition 0, this compartment 0 having an aperture 0 adjacent to thesaid partition opening to the atmosphere. On a piston rod 70 are securedpis tons 70 and 70 working respectively in the compartment 0 and thechamber A and a slide S working in the central chamber B is operativelyconnected with the said rod. A light spring 0 pressing on the piston ktends to keep the piston system in the position shown in the drawing.The space E is in communication through a pipe I) with the space B inthe container H The usual auxiliary reservoir H, which is incommunication with the train pipe L through a non-return valve R is alsoin communication with the space A through a non-return valve R and apipe (Z leads from this reservoir H to an opening in the casing of thevalve S6 which is normally closed by the slide S A pipe 0 leading fromthe brake cylinder C opens into the casing of the valve S6 adjacent to ahole 0 which is an outlet to the atmosphere, and when the hollow part ofthe slide S is in the position illustrated the brake cylinder canexhaust through the hole 0 A branch pipe at from this pipe 0 opens intothe compartment 0 V The. small counterpiston 70 ensures that thepressure in the chamber A is in proportionto the loaded piston areagreater than in the chamber B, except that equality of pressures mayexist when the brake is fully applied. When filling and when completelyreleasing the brake the overflow of the compressed air from the chamberB which is filled by the train pipe L through the control valve St tothe chamber A, takes place around the sleeve of the piston K. Thepurpose of the arrangement of the differential piston K7c in theregulating container is to facilitate a stepped or graduated release ofthe brake in the following manner :-If after an application of the brakethe pressure in the train pipe L 1s somewhat increased, but not to themaximum pressure of 5 atmospheres, in order to reduce the braking effectwithout fully releasing the brake, the augmented train pipe pressuretends to press the control piston 70 with its slide S into the positionof release as shown inFigure 1. Consequently compressed air passesthrough the pipes L and 6* to the chamber B and produces an increase ofpres sure therein, whereby the pistons K7c-" are pressed towards theleft hand side, but the effective surface of the back: of the piston Kbeing smaller than that of its front or right hand side to the extent ofthe cross sectional area of the'rod 72 and the piston 70*, in thecondition of equipoise the air in the chambers A and A is more stronglycompressed than in the chamber B, that is to say, a higher pressure thanprevails in the chambers A and A than in the chamber B and train pipe L.This presurecauses the piston 70 and slide S to be forced somewhattowards the left hand side again, when the slide S closes the mouth ofthe pipe L If no further compressed air is admitted to the pipe L, thepis ton k and slide S remain standing in the position to which they havethus been moved no more compressed air reaches the chamber B, and thecontrol valve is in the partially released position.

In this manner the complete graduation of the pressure in chamber B isassured both in the increase and the decrease of the said pressure.

The space E above the control piston K is subjected to the pressureprevailing for the time being in the space B of the regulating containerH The spring 0 conjointly with the pressure loading the upper side ofthe piston I. 11 holds the slide valve S of the control valve in thatposition in which, when the brake is released, the brake cylinder C isconnected with the aperture 0 leading to the atmosphere. In the spaceunder the small piston is air is released. This piston 7c is not underpressure when the brake is released. l/Vhen braking the compartment 0 isfilled at the same pressure as that existing in the 'brakecylinder C.

Every reduction of the pressure in the main pipe causes, because of thesensitiveness of the control piston in the control valve St itsdisplacement in the direction of the train pipe connection L thereby thechamber B of the regulating air container H is connected through 0 withthe atmosphere. The pressure in chamber 13 of the secondary controlvalve S25 falls at the same rate as the in the chamber 13. This pressuredecrease in'the chamber B permits expansion of the air in the chamber Aofthe regulating air container. 'Should the pressure in the trainpipe bereduced only a small amount and the pipe exhaust be then closed bymoving the drivers' brake" valve into the closed position, thepressureinthespace soon tallsbelow that inthe pip'eL, and the train pipepressure moves the slide S of the control valve. Szf into the closingposition,in

which the aperture 0 leading to the atmosphere is closed. Owing to thefact that the pressure in B and B 'has fallen, a movement of thedifierential piston Z2 Z3 in the control valve Si -occurs under theinfiuen'ceoit the compressed air enclosed in the chamber 23; if thecapacity of this chamber A is sufticient, the 'air therein only expandsslightly. The said movement of the difierential piston occurs in such amanner, that the slide valve S closes the aperture 0 leading totheatmosphereand connects the passages d and V c and thus also theauxiliary air reservoir H, with the brake cylinder C. The increasingpressure developing in the latter act-s on the small pistonk and movesit to close the pipe (Z without bringing about a connection between 0and O? that would release the air from the brake cylinder, because ofthe gradually decreased braking effect and li nally a completefreleaseof thebralre;

Lea-kages of compressed air from the brake cylinder are automaticallycompensated in the following manner :Assuming that on the application ofthe brake the pressure in the chamber B has fallen below the train pipepressure owing to the escape of air through the pipe 6 and the outlet 0,until therestored train pipe pressure has pushed back the piston andslide S to cut off the communication between 6 and O, and that the brakecylinder pressure actingin the chaniher 0 on the piston is has sodisplaced the slide S that the connection between 0 and d? isinterrupted, n'ow if air escapes from the brake cylinder'through a leakypart thereof, the reduced pressure in the brake cylinder causes areduction of pressure acting on the piston I0 The. pressure in thechamber A} isthen able to lift the piston Z5 and slide S sufliciently toreconnect 0Z and'o so that com.- pressed air again fiows from theauxiliary reservoir to the brake cylinder. The consequent rise ofpressure in the brakecylinder isat the same time exerted onthe piston Z5which thus moves the slide S to interrupt the connection between (Z and0 Thus it a will be seen that automatic compensation for the brakecylinder C, connects the said cylinder with the primary control valve Stwhen braking. a a

The air release of the brake cylinder has in this embodiment beenallotted to the secondary and primary control valves. Thefilling grooven in this embodiment provides for the filling of the container H If thebraking operation is started by a' re duction of the train pipepressure, then the connection fO is-broken by theslide S of the primarycontrol valve SF, and the connection between the regulating container Hand the pipes e and c is established. The brake cylinder C is thereforefirst of all supplied with compressed air from the regulating containerH through a non-return valve R By reason of the reduction of the pressure in the container H the pressure falls in the chamber 13 of thesecondary control valve S6 the pressure prevailing in the controlchamber A 'displaces the control piston unit7c 71: and'therebyestablishes the connection between the ducts di and c and also betweenthe auxiliary air reservoir H and the brake cylinder C. If the pressurein B falls below the pressure in the train pipe L when the exhaust ofair in the train pipe L is interrupted by means of the drivers valve, onthe locomotive thenthe primary control valve St is moved into therelease position. The eiiect of the brake cylinder pressure on the smallpiston 10 and thus also, on the secondary control valve is the same asalready described with regard to the example repvoir'for the primarycontrol valve and'the brake cylinder. In this modification the controlbhamber A? of? the secondary control valve S6 is connected 'withithecontainer H and this connection is governed on the one hand by thesecondary slide valve S and on the other hand by a valve '1), openingtowards the control'chamber A which valve is provided with a hole orby-pass m-to render it sensitive. The difierential' piston is, Z2

tha governs the motion of the slide valve S in the secondary controlvalve is in this modification of the brake divided in such a manner,that the smaller piston which is inilucnced by the pressure of the brakecylinder, when bra-king, does not, in its normal position, act on theslide valve. The two control valves are arranged in such a manner, thateach of them, when braking is going on, supplies the compressed air fromthe container H to a pipe 5 leading to the brake cylinder, in which pipea throttled or constricted part D determining the rise of pressure inthe brake cylinder is incorporated. The function of the valve 41 is tomaintain the pressure in the control chamber A as far as possible at thesame level. lVhen equal pressures exist in the chambers A and H that is,when the brake is released, then the valve 1; is kept in such a positionby a light spring 4: of only suflicient strength to carry its weight,that the small aperture m in the cylindrical extension of the valve bodyeffects the connection between A and B WVhen the brake is applied andthe pressure in the container H falls, the valve m is closed by thepressure in the chamber A \Vhen filling the spaces A and B (that is tosay when'the brake is released) the parts occupy the positionsrepresented in Figure 3. The filling of the container H is effectedthrough the non-return valve R and the filling groove n. This fillinggroove determines at the same time the required non-sensitiveness of thecontrol valve St as regards possible leakages and the like.

If the ebntroipistonkl is displaced to the right during braking, inconsequence of the drop of pressure in the train pipe, the opening 0leading to the atmosphere is then closed, and simultaneously the mouthof the duct 6 leading to the brake cylinder C is opened so that airflows from H through 5 and b to the brake cylinder C. This causes a dropof the pressure in the container H; the pressure existing in the chamberA cannot quickly equalize itself with the pressure in H through thenarrow hole m of the valve '0, and closes the said valve '2). Thecontrolling piston is is moved .to the left through the pressure of thechamber A in doing this, it first of all traverses a distance whichcorresponds to the space or play be tween the rods of the pistons k andis, and the slide S thereby closes the mouth of the duct 9 and opens themouth of the duct 6 so that compressed air flows to the brake cylinderfrom this side also. When the exhaust of train pipe air is interruptedby placing the drivers brake valve upon the locomotive in the brakerelease position, then the pres sure in the regulating container H againfalls for the time being; if it has fallen be low the train pipepressure, then in the primary controlling valve the controlling slide Sis pushed back into the release position.

If the latter is the case, then no compressed air can escape from thebrake cylinder, because the control slide S holds the connection betweend and 6 closed. When the pressure in the brake cylinder has reached issomewhat to the right, so that the mouth of the duct 5 is covered. Now,should the pressure in the brake cylinder fall owing to a leakage in thepiston, then the pressure in the chamber 0 will also fall, the pistons7c and 70 move somewhat to the left and, through the duct 6 thus exposedsome compressed air will again flow into the cylinder until the originalpressure has again been attained therein. Hence, also in thisconstructional form compressed air losses in the cylinder areautomatically made good.

If it is intended to diminish the braking effect by a certain amount,then the slide S of the primary control valve is pressed into thereleased position by means of the increase of the pressure in the trainpipe. As a consequence the pressure in the container H increases. Thedifference of pressure on the two sides of the piston 70 becomessmaller, and the loading spring of the piston is in conjunction with thebrake cylinder pressure pushes the piston system to the right. The slidevalve S connects b with d, and as (Z is already connected with O, thebrake cylinder air escapes to the atmosphere. The pressure acting uponthe left side of the piston 70 is therefore reduced; as the pres sure inthe container H is not being increased to the amount corresponding tothe complete release of the brake, the pressure prevailing in thechamber A pushes the piston 70 somewhat to the left so that the channel6 is closed. 1

lVhen the brake is completely released the pressure in the container His increased to its maximum amount of 5 (five) atmospheres, whereby thechannel 9 is opened and the chamber A is also filled with air up to thefull pressure, should any leakage have occurred therein.

The embodiments described above differ considerably from the standardsingle chamber brakes of known types in regard to the arrangement of theprimary control valve in relation to the brake cylinder and theauxiliary reservoir, and in that the graduating slide in the primarycontrol valve is absent. If it is desired to convert the standard singlechamber brake of known type, while re taining its essential characterand the aforesaid arrangement of the parts in relation to each other,into a brake according to'the principles of this invention, this can beeffected by the arrangement represented diagrammatically in Figure 4.This figure illustrates, if the parts added by the conversion are forthe moment neglected, the generally known arrangement of a singlechamber brake, wherein the brake cylinder C is arranged on one side ofthe container H acting both as auxiliary reservoir and regulatingcontainer,.to the other side of which is fitted as a primary controlvalve the standard control valve S6 with a bottom slidevalve S a.graduating slide valve 8 and a filling groove These parts are thusretained unaltered It is only necessary to add for the conversion thesecondary control valve S6 an intermediate piece Z interpolated betweenthe primary control valve St and the container H and the pipe (Zconnectedwith the exhaust opening 0 which leads to the slide valve S? ofthe secondary control valve S25 which pipe (Z is in the releasepositionconnected by means of the slide valve S with the additionalexhaust opening 0 A four way cock U is arranged in the intermediatepiece Z and is provided with several passages of different diameters soas to enable the brake to be adapted for use with, goods trains aswellas passenger trains.

In order that the emptying of the brake cylinder, when the brake isbeing released, may be efiected independently ofthe passage at the timein use inthe cock U which determines the rise of the brake pressure, aduct 1' controlled by the check valve R is provided. 1 v

In the drawing the connection between the brake cylinder C and thechamber 0 of the secondary control valve S16 is represented as a pipeissuing from the brake cylinder, also the connection between thecontainerI-I and the compartment 0 of the secondary control valve isimmediatelyconnected to the brake cylinder. This method ofrepresentation is adopted for the purpose of making the conditionseasily comprehensible. For the purpose of avoiding any unnecessaryalterations of the parts of the single chamber brake when transformingfrom the normal type, the chamber 0 to be filled with air at thepressure of the brake cylinder, will be connected as near as possible tothe connection of the pipe 7' leading to the intermediate piece Z, andthe connection between B and H will also be placed as close as possibleto the corresponding opening in the intermediate piece Z.

Devices for causing the rapid transmission of the pressure drop in thepipe when the latter is opened by the drivers brake valve for thepurpose of actuating the brake, and devices for throttling the flow ofcompressed air to the brake cylinder after the application of the brakeshoes to the wheels, are preferably so arranged, that they arecontrolled by the primary control valve.

A minimum pressure valve acting in the manner known per se is ifrequired arranged on the intermediate piece Z.

The working of a single chamber brake converted in the manner describedin reference to Figure 4 corresponds with that of the brakes representedin Figures 1 to 3.

c It will be understood that the air connections illustrated anddescribed as pipes may in certain constructional embodiments be formedas ducts through solid portions of the ing an easily moving pistonhighly sensitive lating container, a primary control valve havtopressure variations, said primary control valve being directly connectedwith said pipe, connections from said primary control valve to saidcontainer adapted to efiect the filling and exhaustion of said containerin accordance with the movements of said piston, a

secondary control valve having a control chamber, a piston reclprocablein said chamber, means operable by said piston to regulate the chargingand discharging of the brake cylinder, connections from said containerand from said cylinder to said secondary control valve whereby thepressures in said container and cylinder respectively are enabled to actin. the same direction on the a piston of said secondary control valvein op position to a pressure in said control chamber.

2. In a single chamber compressed air brake, a train pipe, a brakecylinder, a regulating container, a primary control valve having aneasily moving piston highly sensitive to pressure variations, saidprimary control valve being directly connected with said pipe,connections from said primary control valve to said container, saidcontrol valve in the release position open-ving communication betweenthe train pipe and said container and in the brake position opening saidcontainer to the atmosphere, a secondary control valve having a controlchamber, a piston reciprocable in said cham ber, means operable by saidpiston to regulate the charging and discharging of the brake cylinder,connections from said container and from said cylinder to said secondarycontrol valve whereby the pressures in said container and cylinderrespectively are enabled to act in the same direction on the piston ofsaid secondary control valve in opposition to a pressure in saidchamber.

3. In a single chamber compressed air brake as in claim 2, connectionsfrom each end of the regulating container to different parts of thecasing ofthe primary'control valve, a slide movable in said casingadapted to place one of said connections in communication with the trainpipe, said slide being adapted when in another position to place saidconnection in communication with the atmosphere. 7 r

. 4. In a single chamber compressed air brake as in claim 2, connectionsfrom each end of the regulating container to different parts of thecasing of the primary control valve, a slide movable in said casingadapted to place one of said connections in communication with the trainpipe, said slide being adapted when in another position to place saidconnection in communication with the atmosphere, and a piston movable insaid container to divide same into two chambers of relatively variablecapacity.

5. In a single chamber compressed air brake, a train pipe, a brakecylinder, a regulating container, a primary control valve having aneasily moving piston highly sensitive to pressure variations, saidprimary control valve being directly connected with said pipe,connections from primary control valve to said container adapted toeffect the filling and exhaustion of said container in accordance withthe movements of said piston, a secondary control valve having a controlchamber, a differential piston device comprising a larger pistonreciprocable in said chamber and adapted to regulate the charging anddischarging of the brake cylinder, said larger piston being exposed tothe pressure in said chamber and also to the pressure in said container,and a smaller pis ton exposed on the side remote from said chamber tothe brake cylinder pressure.

6. In a single chamber compressed air brake, a train pipe, a brakecylinder, a regulating container, a primary control valve having aneasily moving piston highly sensitive to pressure variations, saidprimary control valve being directly connected with said pipe,connections. from said primary control valve to said container adaptedto effect the filling and exhaustion of said container in accordancewith the movements of said piston, a secondary control valve having acontrol chamber, a differential piston device comprising a larger pistonreciprocable in said chamber and having a slide adapted to regulate thecharging and discharging of the brake cylinder, said larger piston beingexposed to the pressure in said chamber and also to the pressure in saidcontainer, and a smaller piston exposed on the side remote from saidchamber to the brake cylinder pressure, the slide of said secondarycontrol valve being adapted to open to V atmospheric pressure the saidremote side of said smaller piston.

7. A single chamber compressed air brake as in claim 5, wherein thedifferential piston device of the secondary control valve is dividedintotwo portions.

8.'In a single chamber compressed air brake as in claim 1, a hollowslide in the secondary control valve movable with the piston thereof, apipe from the brake cylinder opening under said slide, another pipehaving one end opening under said slide and its other end opening undera hollow slide in the primary control valve, the piston of which lattervalve is adapted to place the hollow of its slide in communication withthe atmosphere, whereby the exhaustion of the brake cylinder can beelfected by the co-operation of the primary and secondary control valvepistons.

9. In a single chamber compressed air brake as in claim 1, connectionsbetween the brake cylinder and the primary control valve, and a slide insaid valve adapted to open said connections when in the brakingposition, whereby-said cylinder can be placed in communication with thecontainer across said primary control valve.

10. In a single chamber compressed air brake as in claim 1, connectionshaving a throttlcd passage between the brake cylinder and the primarycontrol valve, and a slide in said valve adapted to open saidconnections when in the braking position, whereby said cylinder can beplaced in communication with the container across said primary controlvalve.

11. A single chamber compressed air brake as in claim 1, wherein theusual auxiliary reservoir is combined with the regulating container asone compressed air vessel in communication with both the primary andsecondary control valves.

12. In a single chamber compressed air brake as in claim 1, a valveprovided with a by-pass in the connection between the reg ulatingcontainer and the control chamber of the secondary control valve.

13. In a single chamber compressed air brake as in claim 1, a connectionbetween the brake cylinder and the primary control valve, a slide insaid valve adapted to open said connection when in the braking position,and a check valve arranged in the said connection.

VILHELM HILDEBRAND.

